1. Field of the Invention
The present invention relates to a solid-state image pick-up device and a manufacturing method thereof; an image pick-up apparatus; a semiconductor device and a manufacturing method thereof; and a semiconductor substrate. In more particular, the present invention relates to a solid-state image pick-up device in which a gettering layer is provided on an upper layer of an element forming layer to suppress metal contamination and a manufacturing method of the solid-state image pick-up device; an image pick-up apparatus; a semiconductor device and a manufacturing method thereof; and a semiconductor substrate.
2. Description of the Related Art
A thin semiconductor device having a high strength, such as a rear surface irradiation type solid-state image pick-up device, has an element forming layer and a wiring layer provided on one surface of the element forming layer. In the element forming layer, photoelectric conversion elements and active elements are formed, and the active elements convert signal charges which are photoelectric-converted by the photoelectric conversion elements into electrical signals and output the electrical signals. In addition, the wiring layer performs wiring of the active elements formed in the element forming layer. Furthermore, it is configured such that visible light is incident on the photoelectric conversion elements from one surface of the element forming layer located at a side opposite to that of the wiring layer (see for example, Japanese Unexamined Patent Application Publication No. 2003-31785).
In order to optimize the spectral balance of color to the photoelectric conversion element when visible light is converted into an electrical signal and also to form a pixel having a desired device structure from a front surface side to a rear surface side, the element forming layer is preferably formed to have a desired small thickness. For example, in the case of a solid-state image pick-up device in which a silicon substrate is used as the element forming layer, the thickness thereof is preferably decreased to 10 μm or less.
As a semiconductor substrate in which elements, such as photoelectric conversion elements and active elements, are formed in a three-dimensional manner, in general, a silicon substrate having an SOI structure is used in which an element forming layer (SOI layer) made of silicon is formed on a silicon substrate functioning as a support substrate with a SiO2 film (BOX layer) interposed therebetween.
Next, with reference to FIGS. 15 and 16, a related example will be described in which a rear surface irradiation type solid-state image pick-up device is formed using a semiconductor substrate which has an SOI structure.
As shown in FIG. 15, a silicon oxide film (SiO2) 102 having a thickness of approximately 1 μm is formed on a surface of a silicon substrate 101 functioning as a support substrate, and an element forming layer 103 having an SOI structure is formed on the silicon oxide film 102. In addition, in the element forming layer 103, there are formed photoelectric conversion elements 104 and active elements (not shown) which convert signal charges photoelectric-converted by the photoelectric conversion elements into electrical signals and which output the above signals. Furthermore, a wiring layer 105 which performs wiring of the active elements is formed on the surface of the element forming layer 103.
In the semiconductor substrate of the solid-state image pick-up device described above, after the elements are formed in the element forming layer 103, and the wiring layer 105 is formed, as shown in FIG. 16, the thickness of the semiconductor substrate is decreased from a rear surface side (visible light incident side), so that only the element forming layer 103 is allowed to remain.
In the semiconductor structure having an SOI structure described above, the silicon oxide film 102 is formed in the semiconductor substrate. Hence, when the thickness of the semiconductor substrate is decreased by wet etching, the etching can be stopped by the silicon oxide film 102. In addition, when the silicon oxide film 102 is subsequently peeled away, only the element forming layer 103 may be allowed to remain.
However, a method for manufacturing a semiconductor substrate including a different type of material (SiO2), such as a semiconductor substrate having an SOI structure, is complicated, and the product obtained by the method described above is expensive. In addition, since a gettering layer is not formed in the element forming layer 103, after the silicon oxide film 102 is removed, it is difficult to prevent metal contamination caused by heavy metals in various processes.
In addition, heretofore, a technique has been proposed in which a structure having a gettering effect against metal contamination is formed in a semiconductor substrate at a rear surface side (for example, see Japanese Unexamined Patent Application Publication No. 6-61235).
However, in the case in which an insulating film is present in a substrate as in a semiconductor substrate having an SOI structure, since the insulating film prevents the diffusion of metals, even when the gettering effect is imparted to a rear surface side of the semiconductor substrate having an SOI structure, the gettering effect described above may not be sufficiently obtained. In addition, in the case in which the thickness of the semiconductor substrate is decreased from a rear surface side thereof so that only an SOI layer is allowed to remain, the gettering layer formed in the semiconductor substrate at a rear surface side is also removed, and hence in a process after the gettering layer is removed, no gettering effect can be obtained.
In addition, another technique is also conceived in which a gettering layer is formed in a deep region of an SOI layer which is close to a BOX layer. However, when the gettering layer is provided in a deep region of the SOI layer, in the case in which elements are formed not only in a surface region of the SOI layer but also in a region thereof in a depth direction, degradation in element characteristics caused by crystalline defects derived from the gettering layer may occur in some cases.
Accordingly, in order to prevent metal contamination and to suppress the degradation in element characteristics, a technique has been proposed in which a gettering layer is provided between an element forming layer in which elements are formed and a thin film-forming removal layer laminated on one surface of the element forming layer (see for example, Japanese Unexamined Patent Application Publication No. 2007-88450).